What is it?

Reverse Snowflake Joins (abbreviated as revj) is a tool to understand SQL and document SQL queries. This is especially good for maintaining big queries written by somebody else. "Big SQL" can be as many as 20 tables, joined by multiple fields.

Parts of the query appear directly in the diagram: Ex age=30 , GROUP BY (year), HAVING MIN(age) > 18 .

Getting these queries right is difficult because many tools generate poor SQL when dealing with complex joins. Manually written SQL is also error-prone, for example one might forget to remove a table if it is no longer needed to filter/group by one field in that table.

If there are disconnected tables it means there is a cartesian product. There are legitimate cases for cartesian products, however these cases are not common.